Burglar alarm



y 23, I N. DEMOSTHENES 2,208,721

BURGLAR ALARM Filed Oct. 17, 1939 2 Sheets-Sheet 1 my. Z

I fiza/m' ismaae eiwks' 1 By 2: a? i ii,

A iiorneys y 1940- N. DEMOSTHENES BURGLAR ALARM Filed Oct. 17, 1939 2 Sheets-Sheet 2 Attorneys Patented July 23, 1940 UNITED STATES PATENT OFFICE 3 Claims.

The present invention relates to new and useful improvements in burglar alarms and has for its primary object to provide, in a manner as hereinafter set forth, an apparatus of this character comprising a control switch of a novel construction and arrangement for closing the circuit to an electric signal, such as a bell, when closed.

Another important object of the invention is to provide a burglar alarm of the aforementioned character which may be conveniently rendered inoperative when desired.

Other objects of the invention are to provide a burglar alarm of the character described which will be comparatively simple in construction,

highly eflicient and reliable in use, compact, inconspicuous and which may be manufactured and installed at low cost.

All of the foregoing and stillfurther objects and advantages of the invention will become apparent from a study of the following specification, taken in connection with the accompanying drawings wherein like characters of reference designate corresponding parts throughout the several views, and wherein:

Figure 1 is a view in side elevation of a burglar alarm constructed in accordance with the present invention.

Figure 2 is a view in vertical longitudinal section through the switch.

Figure 3 is a topplan view of the switch.

Figure 4 is a perspective view of the switch plunger anchoring means.

Figure 5 is a cross sectional view, taken substantially on the line 55 of Fig. 2.

Figure 6 is a detail view in perspective of the switch lock.

Figure 7 is a diagrammatic view of the electric circuit.

Referring now to the drawings in detail, it will be seen that the embodiment of the invention which has been illustrated comprises an elongated casing which is designated generally by the reference numeral I, said casing being of any suitable electricity insulating material. The casing I is firmly mounted on a suitable support 2, such as a wall, through the medium of brackets 3. As best seen in Fig. 2 of the drawings, the casing I has formed longitudinally in its upper and lower walls slots 4 the purpose of which will be presently set forth.

The reference numeral 5 designates a conventional transformer which may be mounted on the wall 2 or at any suitable point. A cord 6 connects the transformer 5 to a source of electricity.

Mounted on the forward end I of the casing I is a contact 8 which is connected by a conductor 9 with the transformer 5. The reference numeral I9 designates an electric bell which may be located at any suitable point, one side of said bell being electrically connected with the transformer 5 by a conductor II. I

Mounted for longitudinal sliding movement in the casing I is a carriage I2 in the form of a vertical bar of suitable material. The bar I2 terminates in reduced end portions I3 constituting guides which are slidable in the slots 4. Extending through the bar l2 and fixed therein is a longitudinally extending plunger I4 of suitable insulating material. Mounted on the forward end of the plunger I4 is a contact I5 which is engageable with the contact 8. A conductor I6 electrically connects the contact I5 with the other side of the electric bell ID.

A coil spring I! encircles the rear end portion of the plunger I I and has one end engaged with the rear wall I8 of the casing land its other end engaged with the bar I2 for yieldingly urging said plunger forwardly. Mounted on the rear Wall I8 of the casing I is an anchor block I9 of any suitable material such as wood. The anchor block I9 is provided with a reduced forward end portion 29 which is engageable in an opening 2! provided therefor in the end wall I8 of the casing I. A snap fastener 22 releasably secures the plunger I 4 in retracted or open position to the anchor block I9 against the tension of the spring I1. The fastener 22 includes a female member or socket 23 which is mounted on the rear end of the plunger I4 and which is adapted to receive a male member or head 24 which is mounted on the forward end of the anchor block I9. The reference numeral 25 designates a flexible strand in the form of a cord, wire or the like having one end connected to the anchor block I9, as at 26. The other end of the strand 25 is secured, as at 27, to a wall, door or the like 28. Pivotally mounted for swinging movement on top of the casing I is a lock 29 which is engageable with the adjacent guide I3 for holding the switch open when the apparatus is not in use.

It is thought that the manner in which the invention functions will be readily apparent from a consideration of the foregoing. With the lock 29 in inoperative position the anchor I9 secures the plunger I4 in retracted position against the tension of the spring I I. Thus, the contact I5 is spaced from the contact 8 and the electric circuit to the bell I0 is open. When the cord or the like 25 is pulled the anchor I9 is detached v for disconnecting same from the from the plunger [4. The plunger l4, thus released, is moved forwardly by the spring I! for engaging the contact 15 with the contact 8, thereby closing the electric circuit and energizing the bell IE. It may be well to here state that any suitable electric signal, such as a light, may be used in lieu of a bell or, if desired, both may be used. The projecting guides i3 permit the plunger M to be readily reset against the tension of the spring ll. If desired, the electric circuit may have interposed therein at any suitable point a manually operable switch for deenergizing the bell 10. One of the side walls 3!] of the casing is removable to permit access to be had to the elements in said casing.

It is believed that the many advantages of a burglar alarm constructed in accordance with the present invention will be readily understood and although a preferred embodiment of the device is as illustrated and described, it is to be understood that changes in the details of construction and in the combination and arrangement of parts maybe resorted to which will fall Within the scope of the invention as claimed,

What is claimed is: l

1. A burglar alarm switch comprising a casing having slots in certain of its opposed walls, a stationary contact mounted in said casing, a carriage slidably mounted in the casing and including guides operable in the slots, a plunger secured, at an intermediate point, on said carriage, a contact on said plunger engageable with the first named contact, a coil spring mounted in the casing and encircling one end portion of the plunger and engaged with the carriage for actuating said plunger toward the first named contact, an anchoring member removably mounted on the casing, means detachably connecting the plunger in retracted position to said anchoring member against the tension of the coil spring, and means connected to the anchoring member plunger for releasing said plunger,

2. A burglar alarm switch comprising a casing having an opening therein, a stationary contact 'mounted in the casing, a carriage slidably mounted in said casing, a plunger mounted on said carriage, a contact on said plunger engageable with the first named contact, a spring for actuating the plunger for engaging the contacts, an anchoring member removably mounted on the casing and including a reduced portion engaged in the opening in said casing, means releasably lin one end wall, a stationary contact mounted on c the other end wall of the casing, a carriage slidably mounted in the casing and including guides projecting through the slots and operable therein, a plunger of insulating material mounted on the carriage and projecting in opposite directions therefrom, a contact on one end of said plunger engageable with the first named contact, a coil spring mounted in the casing and encircling one end portion of the plunger, said coil spring being engaged with the carriage for yieldingly urging said carriage and the plunger toward the first named contact, an anchoring member removably mounted on the casing and including a reduced portion engaged in the opening, a head and socket fastener detachably securing the plunger in retracted positionto the anchoring member against the tension of the coil spring, and flexible means connected to the anchoring member for discon necting said anchoring member from the plunger for releasing said plunger.

NICHOLAS DEMOSTI-IENES. 

